A projector projects light from a light source as modulated by a spatial light modulator or object to form an image on a viewing surface. The image is made up of pixels spatially arranged to form an image. Each pixel is created with color characteristics such that an image formed by the properly spatially arranged pixels corresponds to an image represented in image data. The pixels are made up of a plurality of projected pixels that are spatially or temporally combined to give the pixel the desired color characteristics. The projected pixels are created in a plurality of colors, typically blue, green and red or blue, green, red and white.
The range of colors that can be represented by combining projected pixels of given colors is known as the gamut. In an idealized projector, the projected pixels might be mono-chromatic, single-wavelength primary colors, for instance, blue, green and red. These colors would combine to make all of the colors possible using the mono-chromatic primary colors.
In reality, projected pixels are not typically monochromatic, but include spectral energy within a spectral band corresponding to the desired color. For instance, blue, green and red projected pixels in a projector could each include light with a spectral power distribution within a color spectral band. For example, a blue spectral band can be centered at about 450 nm, a green spectral band can be centered at about 550 nm and a red spectral band can be centered at about 700 nm. The color spectral bands can be, for example, about 80 nm wide. The color spectral bands of projected pixels of a given projector are generally determined by the characteristics of the specific modulator used with the projector.
A light source for a projector has a characteristic spectral energy distribution. The light includes energy at a range of frequencies distributed throughout the visible spectrum. The modulator will permit light from the light source falling within a particular color spectral band to be included in projected pixels of that color. The spectral power distribution of light in the projected pixel will correspond to the spectral power distribution of the light source within that spectral band.
Where color projected pixels are not mono-chromatic, but have spectral power distributions within the color spectral bands, the gamut is less than optimal. This is because each projected pixel alone corresponds to a mix of colors at frequencies distributed throughout the spectral band. The gamut is correspondingly smaller.